Methods of forming electrically conductive pathways using palladium aliphatic amine complexes

ABSTRACT

An ink-jettable composition including a palladium aliphatic amine complex solvated in a liquid vehicle can be used in formation of electronic devices. The ink-jettable composition containing a palladium aliphatic amine complex can be jetted onto a substrate in a predetermined pattern. A second composition can also be applied to the substrate using ink-jet printing or other printing techniques, wherein the second composition is applied onto at least a portion of the predetermined pattern. The second composition can include a reducing agent which is capable of reducing the palladium aliphatic amine complex to palladium metal, typically upon the application of heat. The described ink-jettable palladium complex compositions can be stable over a wide range of conditions and allow for the formation electronic devices on a variety of substrates.

FIELD OF THE INVENTION

The present invention relates generally to printing of circuitry. Morespecifically, the present invention relates to forming conductivepatterns using ink-jet technology.

BACKGROUND OF THE INVENTION

Computer printer technology has evolved to a point where veryhigh-resolution images can be transferred to various types of media.Ink-jet printing involves the placement of small drops of a fluid inkonto a media surface in response to a digital signal. Common ink-jetprinting methods include thermal ink-jet and piezoelectric ink-jettechnologies. Typically, the fluid ink is placed or jetted onto thesurface without physical contact between the printing device and thesurface. There are several reasons that ink-jet printing has become apopular way of recording images on various media surfaces, particularlypaper. Some of these reasons include low printer noise, capability ofhigh-speed recording, and multi-color recording. Additionally, theseadvantages can be obtained at a relatively low price to consumers.

Production of circuits and conductive traces has been accomplished inmany different ways. Further, various methods for manufacturing printedcircuit boards are known. Typical methods for manufacturing printedcircuits include print and etch, screen printing, and photoresistmethods, e.g., applying photoresist, exposing, and developing.Frequently these methods involve considerable capital costs andrestrictions on production times. In recent year, ink-jet technologieshave been used to form circuitry. These ink-jet technologies include avariety of methods which have met with varying degrees of success. Someof these methods involve ink-jetting of a precursor material which aidsin deposition of conductive metals. Other methods involve printing ofconductive inks onto a substrate. Each of these methods hasdisadvantages which limit their effectiveness, such as expense,reliability, and complexity. Accordingly, investigations continue intodeveloping improved circuit fabrication techniques and compositions foruse in ink-jet technologies.

SUMMARY OF THE INVENTION

It has been recognized that it would be advantageous to developinexpensive and simple methods for forming conductive patterns, such ascircuits.

In one aspect of the present invention, an ink-jettable compositioncomprises a palladium aliphatic amine complex solvated in a liquidvehicle.

Another aspect of the present invention includes a method of forming anelectrically conductive pathway using ink-jet technology andink-jettable compositions. A first ink-jettable composition can bejetted onto a substrate in a predetermined pattern. The firstink-jettable composition can include a liquid vehicle and a palladiumaliphatic amine complex solvated therein. A second compositioncontaining a reducing agent can be applied onto at least a portion ofthe predetermined pattern. Heat can then be applied to the predeterminedpattern sufficient to cause reaction between the reducing agent and thepalladium aliphatic amine complex to form palladium metal withoutsubstantially altering the substrate.

Yet another aspect of the present invention includes a system forprinting conductive patterns on a substrate using ink-jettablecompositions having a first printhead, a second printhead, and a heatingapparatus. The first printhead includes a first firing chamber reservoircontaining a first ink-jettable composition including a palladiumaliphatic amine complex. The second printhead can have a second firingchamber reservoir containing a second ink-jettable composition includinga reducing agent, which can be overprinted or underprinted on asubstrate with respect to the palladium aliphatic amine complex. Theheating apparatus can be configured to be in thermal contact with thesubstrate.

Additional features and advantages of the invention will be apparentfrom the detailed description which illustrates, by way of example,features of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

Before particular embodiments of the present invention are disclosed anddescribed, it is to be understood that this invention is not limited tothe particular process and materials disclosed herein as such may varyto some degree. It is also to be understood that the terminology usedherein is used for the purpose of describing particular embodiments onlyand is not intended to be limiting, as the scope of the presentinvention will be defined only by the appended claims and equivalentsthereof.

In describing and claiming the present invention, the followingterminology will be used.

The singular forms “a,” “an,” and “the” include plural referents unlessthe context clearly dictates otherwise. Thus, for example, reference to“a reducing agent” includes reference to one or more of such materials.

As used herein, “liquid vehicle” is defined to include liquidcompositions that can be used to carry a palladium aliphatic aminecomplex, a reducing agent, and optionally, colorants to a substrate.Liquid vehicles are well known in the art, and a wide variety of inkvehicles may be used in accordance with embodiments of the presentinvention. Such liquid vehicles may include a mixture of a variety ofdifferent agents, including without limitation, surfactants, solvents,co-solvents, buffers, biocides, viscosity modifiers, stabilizing agents,and water. Though a variety of agents are described that can be used,the liquid vehicle, in some embodiments, can be simply a single liquidcomponent, such as water.

As used herein, “aliphatic” refers to hydrocarbons having straight orbranched carbon chains. For example, a compound containing an aromaticring is not considered an aliphatic compound. Similarly, compoundscontaining carboxyl groups such as amino acids and other carboxylicacids are not considered aliphatic compounds for purposes of the presentinvention.

As used herein, “complex” refers to a metal having one or more organiccompounds associated therewith via bonds which can be ionic or covalentin nature. The nature of the bond is typically governed by the electronaffinities of the respective components and the surrounding pH, and mayhave characteristics of both ionic and covalent bonds.

As used herein, “primary amine” refers to amines having two hydrogenatoms bonded to the nitrogen of the amine group(s). Complexing agents ofthe present invention can have multiple primary amine groups which caninteract and complex with palladium.

As used herein, “solvated” refers to when a solute is dissolved into asolvent. A compound that is solvated indicates that at least a portionof the compound is dissolved into solution and does not necessarilyindicate that all of the solute molecules are in solution.

As used herein, “electroless deposition” refers to any chemicaldeposition process as opposed to an electrodeposition process.Typically, electroless deposition processes involve acid bathscontaining metal ions, however other such processes known to thoseskilled in the art are considered within the scope of the presentinvention.

Concentrations, amounts, and other numerical data may be presentedherein in a range format. It is to be understood that such range formatis used merely for convenience and brevity and should be interpretedflexibly to include not only the numerical values explicitly recited asthe limits of the range, but also to include all the individualnumerical values or sub-ranges encompassed within that range as if eachnumerical value and sub-range is explicitly recited. For example, aweight range of about 1% to about 20% should be interpreted to includenot only the explicitly recited concentration limits of 1% to about 20%,but also to include individual concentrations such as 2%, 3%, 4%, andsub-ranges such as 5% to 15%, 10% to 20%, etc.

Palladium Aliphatic Amine Complex

In accordance with the present invention, an ink-jettable compositioncan include a palladium aliphatic amine complex solvated in a liquidvehicle. The palladium aliphatic amine complex can be formed using avariety of aliphatic amine complexing agents. Suitable aliphatic aminecomplexing agents are typically aliphatic polyamines such as diaminealkanes. Aliphatic polyamines such as triamine alkanes can also be usedas a complexing agent. In one detailed aspect of the present invention,the complexing agent can be a primary polyamine. Specific non-limitingexamples of such complexing agents include 1,2-diaminopropane,1,3-diaminopropane, diethylenetriamine, 1,4-diaminobutane,1,6-diaminohexane, N,N′-dimethyl-1,3-propanediamine,N,N,N′,N′-tetramethylethylenediamine, 2-hydroxy-1,3-diaminopropane, andmixtures thereof. Other aliphatic amine complexing agents can also beused, such as straight chained and branched aliphatic amines having upto about 20 carbon atoms. Further, the aliphatic amine complexing agentscan have other substituents groups including halogens such as chlorideor bromide, hydroxy groups, or the like. In one embodiment of thepresent invention, the complexing agent can be a diamine such as1,2-diaminopropane. The palladium complex formed with 1,2-diaminopropane is shown below in a cis configuration, although the trans isomeris also typically present.

The palladium complex shown above has a positive charge of 2, and thus,a counter ion is generally present in solution. Typical counter ionsinclude, without limitation, acetate, halides, sulfates, and mixturesthereof. Frequently, the counter ion is chloride, as a common palladiumsource used to produce the palladium complex is palladium chloride. Thepalladium complexes suitable for use in the present invention are stableover a wide range of pH. For example, palladium 1,2-diamino propane isstable and does not precipitate out of solution from a pH of about 2 toabout 12. Other specific complexing agents may vary in stability. Forexample, tetramines are stable from a pH of about 6 to about 7. The widerange of pH stability for various complexing agents allows forsignificant latitude in formulating ink-jettable compositions which aretailored to various ink-jet pens, including thermal or piezoelectricprinting systems. For example, in some embodiments it may be desirableto print the palladium complex with a colored ink composition, such asby simultaneous printing, overprinting, or underprinting with respect tothe palladium ink-jet composition. Frequently, such color inkcompositions involve pH driven bleed control mechanisms. Theink-jettable compositions of the present invention can be easilyincorporated into such systems. Further, specific printhead andsubstrate materials may be more or less resistant to corrosion whenexposed to compositions at various pH levels. In addition to a wide pHstability region, the palladium complexes of the present invention aretypically present in solution. As a result, kogation and cloggingproblems are reduced compared to colloidal suspensions of palladium orother metals.

In one detailed embodiment, the ink-jettable composition contains excessnon-complexed amine. The presence of excess complexing agent canincrease the long-term stability of the composition. In the presence ofexcess complexing agent, the ink-jettable composition can be stableindefinitely. One factor in designing ink-jet compositions is thelong-term stability of the composition in an ink-jet pen. An ink-jetcomposition which is stable, i.e., does not have components whichreadily settle or precipitate, can reduce clogging of the pen nozzlesand improve performance of the ink-jet pen. Thus, it is often desirableto keep the components of the ink-jettable composition in solution forextended periods of time. The ink-jettable compositions of the presentinvention can include from about 2 wt % to about 28 wt % of palladiumcomplex amine. For example, if the complexing agent is1,2-diaminopropane, concentrations of from about 0.1 M to about 1.5 M(saturation at room temperature) can be used.

The ink-jettable composition can include a variety of components such asthose typically used in ink-jet liquid vehicles, such as, but notlimited to solvents, cosolvents, surfactants, biocides, buffers,viscosity modifiers, sequestering agents, colorants, stabilizing agents,humectants, water, binders, and mixtures thereof. Typically theink-jettable compositions of the present invention have a viscosity offrom about 0.8 to about 8 cPs. In one aspect of the present invention,the liquid vehicle can comprise from about 70% to about 98% by weight ofthe ink-jettable composition.

As described, cosolvents can be included in the ink-jettablecompositions of the present invention. Suitable cosolvents for use inthe present invention include water soluble organic cosolvents, but arenot limited to, aliphatic alcohols, aromatic alcohols, diols, glycolethers, poly(glycol) ethers, lactams, formamides, acetamides, long chainalcohols, ethylene glycol, propylene glycol, diethylene glycols,triethylene glycols, glycerine, dipropylene glycols, glycol butylethers, polyethylene glycols, polypropylene glycols, amides, ethers,carboxylic acids, esters, organosulfoxides, sulfones, alcoholderivatives, carbitol, butyl carbitol, cellosolve, ether derivatives,amino alcohols, and ketones. For example, cosolvents can include primaryaliphatic alcohols of 30 carbons or less, primary aromatic alcohols of30 carbons or less, secondary aliphatic alcohols of 30 carbons or less,secondary aromatic alcohols of 30 carbons or less, 1,2-diols of 30carbons or less, 1,3-diols of 30 carbons or less, 1,5-diols of 30carbons or less, ethylene glycol alkyl ethers, propylene glycol alkylethers, poly(ethylene glycol) alkyl ethers, higher homologs ofpoly(ethylene glycol) alkyl ethers, poly(propylene glycol) alkyl ethers,higher homologs of poly(propylene glycol) alkyl ethers, lactams,substituted formamides, unsubstituted formamides, substitutedacetamides, and unsubstituted acetamides. Specific examples ofcosolvents that can be used in the practice of this invention include,but are not limited to, 1,5-pentanediol, 2-pyrrolidone,2-ethyl-2-hydroxymethyl-1,3-propanediol, diethylene glycol,3-methoxybutanol, and 1,3-dimethyl-2-imidazolidinone. Cosolvents can beadded to reduce the rate of evaporation of water in the composition tominimize clogging or other properties of the composition such asviscosity, pH, surface tension, optical density, and print quality. Thecosolvent concentration can range from about 0 wt % to about 50 wt %,and in one embodiment can be from about 15% to about 30% by weight.Multiple cosolvents can also be used, wherein each cosolvent can betypically present at from about 2% to about 10% by weight of theink-jettable composition.

Various buffering agents can also be optionally used in the ink-jettablecompositions of the present invention. Typical buffering agents includesuch pH control solutions as hydroxides of alkali metals and amines,such as lithium hydroxide, sodium hydroxide, and potassium hydroxide;and other basic or acidic components. If used, buffering agentstypically comprise less than about 10% by weight of the ink-jettablecomposition.

In another aspect of the present invention, various biocides can be usedto inhibit growth of undesirable microorganisms. Several non-limitingexamples of suitable biocides include benzoate salts, sorbate salts,commercial products such as NUOSEPT (Nudex, Inc., a division of HulsAmerica), UCARCIDE (Union Carbide), VANCIDE (RT Vanderbilt Co.), andPROXEL (ICI Americas) and other known biocides. Typically, such biocidescomprise less than about 5% by weight of the ink-jettable compositionand often from about 0.1% to about 0.25% by weight.

In one aspect of the present invention, the ink-jettable compositionscan optionally contain surfactants. However, such components can be usedand may include standard water-soluble surfactants such as alkylpolyethylene oxides, alkyl phenyl polyethylene oxides, polyethyleneoxide (PEO) block copolymers, acetylenic PEO, PEO esters, PEO amines,PEO amides, and dimethicone copolyols. If used, surfactants can be from0.01% to about 10% by weight of the ink-jettable composition.

Reducing Agent

As described, the ink-jettable compositions containing a palladiumcomplex can be ink-jetted onto a substrate in a predetermined pattern.The predetermined pattern can correspond to a conductive pathway such asa circuit, a portion of a circuit, or other electronic device. Uponink-jetting the palladium complex onto a substrate, the palladiumgenerally remains in solution, and even upon drying, will not be reducedto palladium metal. Thus, a second composition including a reducingagent can be applied onto at least a portion of the predeterminedpattern. The reducing agent reacts with the non-conductive palladiumcomplex to produce conductive palladium metal. Thus, in someapplications, it may be desirable to only apply reducing agent toportions of the palladium complex printed on the substrate. Further,portions of the palladium can be reduced to palladium metal followed byfurther steps which react or utilize the palladium metal, but do notaffect the palladium complex not having reducing agent applied thereto.At a later step, the remaining palladium complex can then be reduced byapplying reducing agent thereto and applying heat as described in moredetail below. In an additional alternative embodiment, the reducingagent can be applied to the substrate prior to printing the palladiumcomplex thereon. In other embodiments, the reducing agent can be appliedto the entire substrate, to only the areas where the palladium aliphaticamine complex is applied.

In accordance with the present invention, a variety of reducing agentscan be utilized to reduce palladium ions to palladium metal. Reducingagents suitable for use in the present invention include, but are notlimited to formic acid, esters of formic acid, formic acid derivatives,hydrazine, alkali metal borohydride, oxalic acid, alkali or alkalineearth sulfites, and mixtures thereof. In one embodiment, the reducingagent can be formic acid or a derivative thereof. The reduction ofpalladium using formic acid produces only gases and the palladium metal,leaving no residual by-products. Other specific examples of suitablereducing agents include, esters of formic acid, e.g., formic acid ethylester; substituted and non-substituted amides, such as formamide andN,N-dimethyl formamide; salts of formic acid, such as sodium formate;and activated formic acids, such as orthoformic acid. As an alternative,it is also possible to carry out the reduction of palladium using a gasas the reducing agent, such as hydrogen, ethylene, propylene,isobutylene, butylene, or other olefins according to processes known tothose skilled in the art.

In accordance with the present invention, the second compositioncontaining the reducing agent can be formulated as an ink-jettablecomposition or applied directly to the substrate using any known methodsuch as immersion, spraying, screen printing, or other printingtechniques. The second composition can further include solvents,cosolvents, surfactants, biocides, buffers, viscosity modifiers,sequestering agents, colorants, stabilizing agents, humectants, water,binders, and mixtures thereof as discussed above in connection with thepalladium complex. In one embodiment, the second composition can includepigment and/or dye colorants which can be used for aesthetic purposes orto identify specific traces. In one aspect of the present inventionwherein the second composition is ink-jettable, the reducing agent cancomprise from about 1 wt % to about 12 wt % of the second composition.The amount of reducing agent, such as formic acid, applied to thepalladium complex printed on the substrate is most often stoichiometricor excess amounts of reducing agent.

Once the reducing agent is applied to the desired portions of thepredetermined pattern, heat can be applied. The amount of heat appliedto the predetermined pattern can be sufficient to cause reaction betweenthe reducing agent and the palladium complex to form palladium metalwithout substantially altering or damaging the substrate. The reductionreaction can occur, albeit slowly, at room temperature and can beaccelerated as heat is applied. Heat can be applied to the predeterminedpattern using almost any heat source. Several exemplary heatingapparatuses which act as heat sources suitable for the present inventioninclude heater bars, heat lamps, heating plates, forced heated air, orother known sources. Typically, temperatures of from about 50° C. toabout 80° C. are sufficient. However, temperatures above this range canbe used if the substrate is configured such that it will not beadversely affected, e.g. mechanical integrity or electronic properties.In one aspect, temperatures of from about 50° C. to about 70° C. with astoichiometric excess of reducing agent can reduce substantially all ofthe palladium complex to palladium metal in less than about 60 seconds.

After application of heat, the palladium can be reduced to theconductive palladium metal. In some embodiments of the presentinvention, the palladium complex can be printed such that a continuouspattern of palladium metal is formed. In such embodiments, no furtherprocessing is required and the printed conductive pathway can be usedand/or incorporated into an electronic device.

Deposition of Conductive Metal

Alternatively, the palladium complex can be printed in a non-continuouspattern of palladium, wherein individual seeds of pattern provide forthe deposition of a conductive metal. The non-continuous pattern can begenerally formed of a series of dots which are sufficiently close thatdeposition of a conductive metal on the seeds or dots will ultimatelyconnect proximate areas to form conductive pathways as desired.Deposition of the conductive metal can be accomplished using a varietyof known techniques such as electroless deposition andelectrodeposition. In one aspect of the present invention, theconductive metal can be deposited using an electroless process.Electroless deposition processes generally involve a substrate having aseed metal such as palladium deposited thereon. The substrate can thenbe immersed or exposed to a solution of a conductive metal salt and areducing agent. Specific electroless plating compositions and conditionscan be chosen by those skilled in the art to achieve various platingrates, thicknesses, and conductivities. As mentioned, those skilled inthe art will also recognize that the palladium complex can also beprinted in a continuous pattern to facilitate electrodeposition of aconductive metal. Any conductive metal can be used in the presentinvention which is capable of being deposited. Several exemplaryconductive metals include copper, gold, palladium, nickel, silver,rhodium, platinum, magnetic alloys such as Co—Fe—B, Co—Ni—P, Co—Ni—Fe—B,Ni—Co, and mixtures and alloys thereof. In one aspect of the presentinvention, the conductive metal can be copper.

The principles of the present invention can be used to apply aconductive metal to a wide variety of substrates. As mentioned above, inaccordance with the present invention, temperatures used in formingconductive pathways are frequently below 80° C. At this relatively lowtemperature, most substrate materials are typically not adverselyaffected. Substrate materials suitable for use in the present inventioncan include, without limitation, ceramics, polymers, cellulose, glass,silicon, and mixtures thereof. For example, the compositions of thepresent invention can be printed on a standard silicon substrate,polyethylene terephthalate (available from E. I. du Pont de Nemours andCompany as MYLAR), polyimides (available from E. I. du Pont de Nemoursand Company as KAPTON), glass, alumina ceramic, or even certain papersin some low power applications. Although the above mentioned substratesare suitable, almost any non-conductive material or flexible ornon-flexible dielectric material can be used as the substrate in thepresent invention. In addition, the methods of the present invention canbe applied to substrates having previously formed electronic circuitsand/or devices thereon using any known method.

The circuits produced in accordance with the principles of the presentinvention can form a wide variety of electronic devices and theresolution and complexity of such pathways are only limited by theink-jet printing technology. Circuit patterns can include, for example,complex circuits, single traces, antennae, or even multilayeredcircuits. Patterns formed using the ink-jettable composition of thepresent invention can have a linewidth of from about 5 micrometers toany practical width. Generally, a width of several millimeters is thewidest practical width; however, wider conductive pathways could beformed depending on the application. Similarly, the conductive pathwaycan have varying thicknesses as measured from the substrate to an uppersurface of the conductive pathway. The thickness of the conductivemetal, if the palladium itself is used to form the conductive elements,can be easily controlled by the ink-jetting process during printing ofthe palladium complex. Likewise, during electroless deposition, thethickness of the conductive metal is governed by the length of time thesurface is exposed to the electroless solution and the particularsolution and concentrations used. Typically, thicknesses of from about0.2 micrometers to about 3 micrometers are desirable for most electronicdevices.

Using the methods described herein, almost any known predeterminedpattern forming an electronic structure can be prepared, such as, butnot limited to, gates, transistors, diodes, resistors, inductors,capacitors, traces, magnets, and other circuit elements. The presentinvention allows the production of a wide variety of devices in a shortperiod of time and with minimal preparation which normally accompaniesstandard lithography techniques of preparing a mask, deposition,etching, etc. Thus, prototypes of complex patterns can be tested andadjusted without time consuming lithography steps.

In one aspect of the present invention, the predetermined pattern can beprinted in multiple layers to form three dimensional structures. Forexample, a first layer containing a predetermined pattern can beproduced by printing the palladium complex and forming a conductivepathway using any of the above described embodiments. A layer ofinsulating or semi-conducting material of a polymeric resin, organicresin, doped ceramic, semiconductor, or the like can be formed over thefirst layer. Most often, the insulating layer can be discontinuoushaving conduits or holes in which additional conductive metal can beplaced. These holes can be formed after the deposition of the insulatingmaterial using standard lithography technologies. A conductive metal canthen be printed using the methods of the present invention, or otherwisedeposited. Often electroless deposition is suitable since the holesleave only selected areas of the underlying predetermined pattern ofconductive metal exposed. Alternatively, the holes can be formed byprinting a material prior to forming the insulating material whichprevents the insulating material or semi-conducting material fromadhering to the predetermined pattern at specific locations. A secondlayer of conductive circuits or pathways can then be printed on theinsulating material using the above principles. This process can berepeated as many times as needed to form a desired multilayer circuit.

System Incorporating Ink-Jettable Compositions

A variety of techniques can be used to form conductive pathways onvarious substrates. In one embodiment of the present invention, a systemfor forming electrically conductive pathways on a substrate comprises afirst printhead, a second printhead, and a heating apparatus. An ink-jetprinter, for example, can be used to propel ink-jet compositions ontosubstrates using resistive heating elements or piezoelectric elementsfor propelling the composition through an overlying orifice plate. Theink-jet compositions can be stored in a reservoir and the compositioncan travel through a set of channels toward the orifice plate. Inconnection with the present invention, the first printhead can have afirst firing chamber reservoir containing a first ink-jettablecomposition. The first ink-jettable composition can include a firstliquid vehicle and a palladium aliphatic amine complex solvated therein,as described previously. The second printhead can have a second firingchamber reservoir containing a second ink-jettable composition. Thissecond ink-jettable composition can include a second liquid vehicle anda reducing agent. It will be understood that the first and secondprinthead can be present on a common orifice plate, although notcommonly done, or on separate orifice plates. Typically, a commonorifice plate configuration would benefit from the use of non-reactiveliquid vehicles in order to reduce clogging. Additionally, the first andsecond printheads can be contained within multiple housings or a singlehousing. Further, a heating apparatus can be placed in thermal contactwith the substrate. The heating apparatus can supply heat to thepredetermined pattern such that the palladium complex is reduced topalladium metal. The heating apparatus can be a heater bar or lampplaced in a heat conductive relationship to the printed substrate.Alternatively, the substrate can be heated using a heating plate orother heating device subsequent to printing the palladium aliphaticamine complex and the reducing agent thereon. The above describedcomponents can be incorporated into flatbed printers or standard ink-jetprinters which have been modified to print on rigid or flexiblesubstrates, such as optical disks or circuit boards. Generally, amodified ink-jet printer would include inserts which securely hold andmove such substrates past the ink-jet printheads.

EXAMPLES

The following examples illustrate the embodiments of the invention thatare presently best known. However, it is to be understood that thefollowing are only exemplary or illustrative of the application of theprinciples of the present invention. Numerous modifications andalternative compositions, methods, and systems may be devised by thoseskilled in the art without departing from the spirit and scope of thepresent invention. The appended claims are intended to cover suchmodifications and arrangements. Thus, while the present invention hasbeen described above with particularity, the following examples providefurther detail in connection with what are presently deemed to bepractical embodiments of the invention.

Example 1

A solution of 0.1 M bis(1,2-diaminopropyl) palladium (II) chloride isprepared in an aqueous liquid vehicle to produce a palladium complexcomposition. A 0.2 M aqueous solution of formic acid is also prepared. Asyringe is filled with the palladium complex composition. A row of dropsare then deposited on each of the following substrates: KAPTON (apolyimide), alumina ceramic, and glass. A second syringe is filled withthe formic acid solution and the solution applied to the same areas asthe palladium complex composition. The substrates are allowed to sit atroom temperature for about thirty minutes wherein no noticeablereduction of palladium is observed. The above process is repeated toproduce three more sample substrates having the palladium complexdeposited thereon. All six of the substrates are then placed on ahotplate and heated to about 70° C. As the water evaporates, blacktraces of palladium form from the palladium complex. A repeat of theabove procedure (with the heating step) without the addition of theformic acid solution does not produce black traces of palladium metal.

Example 2

To 10 g of deionized water is added 10 g of 0.2 M bis(1,2-diaminopropyl)palladium (II) chloride. To this solution 1 g of2-methyl-1,3-propanediol (MP diol) and 1 g of 1,2ethylhydroxy-2-pyrrolidone is thoroughly stirred. About 0.01 g ofbiocide is then added to form an ink-jettable composition of palladiumcomplex. A reducing agent composition is prepared by adding 1 g of2-methyl-1,3-propanediol and 1 g of 1,2 ethylhydroxy-2-pyrrolidone to 20g of 0.2 M formic acid. These ink-jettable compositions are placed intoseparate ink-jet pens and placed in a standard ink-jet printer. Afterprinting a desired circuit pattern on a glass substrate, the substrateis heated to about 70° C. for about 2 minutes to form a pattern of dotsto be used as seed for electroless deposition of copper. The substrateis then immersed in an electroless copper plating bath (Envision EC-2132available from Enthone, Inc.) for 30 minutes to form conductivepathways.

It is to be understood that the above-referenced arrangements areillustrative of the application for the principles of the presentinvention. Numerous modifications and alternative arrangements can bedevised without departing from the spirit and scope of the presentinvention while the present invention has been shown in the drawings anddescribed above in connection with the exemplary embodiments(s) of theinvention. It will be apparent to those of ordinary skill in the artthat numerous modifications can be made without departing from theprinciples and concepts of the invention as set forth in the claims.

1. A method of forming an electrically conductive pathway, comprisingsteps of: a) jetting a first ink-jettable composition onto a substrate,said first composition including a first liquid vehicle and a palladiumaliphatic amine complex solvated therein; b) overprinting orunderprinting a second composition with respect to at least a portion ofthe first ink-jettable composition to form a predetermined pattern, saidsecond composition including a second liquid vehicle and reducing agentsolvated therein; and c) applying heat to the predetermined patternsufficient to cause reaction between the reducing agent and thepalladium aliphatic amine complex to form palladium metal withoutsubstantially altering the substrate.
 2. The method of claim 1, furthercomprising depositing a conductive metal onto the palladium metal. 3.The method of claim 2, wherein the conductive metal is selected from thegroup consisting of copper, gold, palladium, nickel, silver, rhodium,platinum, Co—Fe—B, Co—Ni—P, Co—Ni—Fe—-B, Ni—Co, and mixtures or alloysthereof.
 4. The method of claim 2, wherein the step of depositing is anelectroless deposition process.
 5. The method of claim 2, wherein thepredetermined pattern is a non-continuous pattern of palladium aliphaticamine complex which, once reduced, is a seed for deposition of theconductive metal.
 6. The method of claim 1, wherein the secondcomposition is underprinted with respect to the first ink-jettablecomposition.
 7. The method of claim 1, wherein the second composition isoverprinted with respect to the first ink-jettable composition.
 8. Themethod of claim 1, wherein the aliphatic amine of the palladiumaliphatic amine complex is selected from the group consisting of diaminealkanes, triamine alkanes, and mixtures thereof.
 9. The method of claim8, wherein the aliphatic amine is 1,2-diaminopropane.
 10. The method ofclaim 1, wherein the substrate comprises a member selected from thegroup consisting of ceramics, polymers, cellulose, silicon, and mixturesthereof.
 11. The method of claim 1, wherein the step of applying thesecond composition is by ink-jetting, said second composition beingink-jettable.
 12. The method of claim 1, wherein the second compositionfurther comprises a colorant.
 13. The method of claim 1, wherein thefirst composition further comprises a colorant.
 14. The method of claim1, wherein the reducing agent is selected from the group consisting offormic acid, esters of formic acid, formic acid derivatives, hydrazine,alkali metal borohydride, oxalic acid, alkali or alkaline earthsulfites, and mixtures thereof.
 15. The method of claim 14, wherein thereducing agent is formic acid.
 16. The method of claim 1, wherein thestep of applying heat occurs at from about 50° C. to about 80° C. 17.The method of claim 1, wherein the predetermined pattern is a circuit.18. The method of claim 1, wherein the first liquid vehicle furthercomprises non-complexed amine.